Roof construction, particularly residential roof construction, varies by climatic location throughout the United States. This invention relates to protective roof coverings formed by roof tiles as opposed to asphalt based roof shingles typically used in the northern parts of the United States to form a protective roof covering. Roof tiles are typically constructed from natural materials such as clay, concrete, stone, ceramics (including brick and fired clay) and have also been made of synthetic material, typically plastic and it is possible to have tiles formed from combinations of natural and synthetic materials, i.e., fibrous cement.
Traditionally, in the United States, roof tiles have been applied with a cementitious material, typically mortar usually mixed at the site. The prior art patents incorporated by reference discuss at length inherent problems encountered when mortar is used to affix roof tiles to the roof substrate and those problems will not be restated herein. However, the prior art patents have not discussed mortar patterns used to affix the roof tiles to the roof. While it may have been conventional at one time to simply place the mortar on the underside of the roof tile, without regard to mortar amount, building construction regulations such as those promulgated by Southern Building Code, Florida, require that no more than 33% of the area underneath the tile be covered by the adhering material. This leaves the space between tiles and between roof and tiles open for air circulation so that the tiles are less likely to be pulled off the roofs during hurricane winds. Accordingly, conventional practice today is to trowel a glob or pad of mortar over the central underside area of the tile (or alternatively, a deposit of the mortar is placed on the roof), which is then flattened somewhat when the tile is positioned onto the roof substrate. Again, the height and area of the mortar pad is such that no more than 33% of the area of the tile is to be covered by the cementitious material. In practice, it sometimes occurs that too little or too much mortar is used which, coupled with the well known adhesive inconsistencies of mortar, results in faulty tile application.
Because of the limitations of conventional cementitious materials, specifically mortar, other types of materials, principally adhesives, have been investigated for use as bonding agents to affix roof tiles to the roof substrate without the need for mechanical fasteners.
A) U.S. Chronology.
Accordingly, at least as early as the summer of 1992, I purchased an off-the-shelf, commercially available, one-component, polyurethane foam in a pressurized aerosol spray type container. The polyurethane foam was applied as a deposit in the shape of a centrally positioned pad, replicating the conventional mortar pad shape and position, and used to affix the roof tiles to the roof. It was found that the polyurethane foam would act as an adhesive fixing the tile to the roof substrate. However, the expansion of the foam lifted the tile as the foam cured and it was believed that the strength of the adhesive bond had to be thoroughly investigated as well as formulations addressing the tile lifting before a commercial product could be offered. Through my employer at that time, Life Tile (a subsidiary of Boral Concrete Products), a number of polyurethane foam companies were contacted to determine if there was an interest in pursuing a joint test program utilizing polyurethane foam as a roof tile adhesive. One company, Poly-Foam Products, Inc. expressed an interest in the roof tile application and I worked with that company commencing in the spring of 1993 on a program which resulted in the development of a two-component, polyurethane roof tile adhesive as disclosed in U.S. Pat. No. 5,362,342, incorporated by reference herein. As is well known, two-component, polyurethane foam is significantly different from a one-component, polyurethane foam. For instance, the chemical reaction of the formulation in a two-component foam occurs when the "A" side (isocyanate) contacts the "B" side whereas a one-component, polyurethane foam undergoes a pre-polymerization reaction within the container and utilizes moisture to effect foaming or frothing as well as curing of the polyurethane. The formulations are markedly different and traditionally the foams, even when sold for the same application, have different characteristics. For example, the two-component foam generally will not expand to the extent of a one-component foam after it has initially foamed on mixing. On the other hand, because of the A/B reaction, a two-component foam will generally have a quicker tack time or shorter open time than a one-component foam. Chemical formulations of the foam, however, can significantly vary such characteristics. In any event, the two-component foam adhesive described in the '342 patent places an adhesive bead extending the length of the tile. While this placement pattern has been tested and approved by the Southern Building Code, Florida for use as a roof-tile adhesive, placing the foam in a bead running the length of the tile is an excessive use of adhesive foam resulting in a higher cost to the roofing contractor than what otherwise is required. Additionally, the two-component application requiring two separate pressurized containers of chemicals, is somewhat unwieldy for use in roofing residential dwellings, especially if the roof pitch is steep.
In late 1995, I began testing a one-component, polyurethane foam supplied by Insta-Foam, Inc. and developed an adhesive pattern to minimize the use of the foam as described in my U.S. Pat. No. 5,895,536. The '536 patent discloses placing two discrete foam deposits (approximately the diameter of a tennis ball) at diagonally opposing corners of the roof tile. As shown in all the embodiments of my patent, one deposit is placed at the leading edge corner of the tile between the roof substrate and the tile underside while the other foam deposit is placed at the trailing edge corner between the outside surface of the lower tile (which the upper tile overlaps) and the underside surface of the upper tile. While less adhesive is used in the system disclosed in the '536 patent when compared to the adhesive used in the system of the '342 patent, two separate deposits are required per tile and only one deposit per tile extends between the roof and tile. This placement fundamentally limits the adhesion ability of the roof system. However, the use of small paddy sizes addressed the issues of tile displacement resulting from expansion during curing at least to the extent that noticeable tile displacement did not occur if the adhesive was properly applied.
The above represents what is believed a chronological development of the utilization of polyurethane foam as a roof tile adhesive in the United States and this is believed consistent with approvals given by building code regulatory agencies of Dade County, Florida which has approved the use of polyurethane foam when placed in a pattern as described in the '342 and '536 patents.
B) Europe.
In Europe, polyurethane foam has long been used to secure roof tiles. For example, an especially fabricated roofing tile having recesses for receiving polyurethane foam is disclosed in UK patent application No. GB 2169329 A, published Jul. 9, 1986. The assignee's sister company has sold a general purpose, one-component, polyurethane foam for use in adhering roof tiles to roofs. A published application of a one-component foam sold in Europe is to place a bead adjacent the leading edge on the outside surface of one tile contacting the trailing edge of the underside surface of a higher tile. Another common application of polyurethane foam is to spray the foam from the inside of the building to fill any cracks between tiles as well as to secure the tiles to longitudinally extending rafters. It is believed that European companies, including assignee's sister company, have sold one-component foams for roofing applications since as early as 1988.
C) Adhesive Application.
Apart from polyurethane foams, special roof tile adhesives have been developed for securing roof tiles to the roof substrate. In particular, Ohio Sealants, Inc. has developed a roof tile adhesive marketed under its Pro Series.RTM. RT600 brand name which has been certified by Dade County for repair of existing roof tiles. Specifically, certified repairs require the removal or the lifting of an existing loose tile sufficient to enable the application of a minimum 1".times.1" bead of adhesive to the existing mortar pad so that both the mortar pad and the under side of the tile are in contact with adhesive and in addition, a 3/8" thick by 2" long bead of adhesive must be applied to the head of the previous tile. Generally, specially formulated, one component, roof sealing adhesives are sold in caulk-type containers which are suitable for repairing existing tiles as opposed to laying courses of tiles covering the entire roof.